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Suggestions for Improving Linux Server Security: Beyond User Permissions and Groups? (lemy.lol)

submitted 2 months ago by [email protected] to c/[email protected]

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Hi all,

I found a hobby in trying to secure my Linux server, maybe even beyond reasonable means.

Currently, my system is heavily locked down with user permissions. Every file has a group owner, and every server application has its own user. Each user will only have access to files it is explicitly added to.

My server is only accessible from LAN or VPN (though I've been interested in hosting publicly accessible stuff). I have TLS certs for most everything they can use it (albeit they're self signed certs, which some people don't like), and ssh is only via ssh keys that are passphrase protected.

What are some suggestions for things I can do to further improve my security? It doesn't have to be super useful, as this is also fun for me.

Some things in mind:

2 factor auth for SSH (and maybe all shell sessions if I can)
look into firejail, nsjail, etc.
look into access control lists
network namespace and vlan to prevent server applications from accessing the internal network when they don't need to
considering containerization, but so far, I find it not worth foregoing the benefits I get of a single package manager for the entire server

threat model

attacker gains shell access
attacker influences server application to perform unauthorized actions
not in my threat model: physical access

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[–] [email protected] 2 points 2 months ago

Get your firewall right then maybe add fail2ban.

You could also consider IDs/IPs on your primary router/firewall if this is internal. If not you can install surricata on a public server. Obviously if you go with something as powerful as surricata you no longer need fail2ban.

Keep a sharp eye on any users with sudo. Beyond that consider docker as others have mentioned.

It does add to security because it allows the developers a bit more control of what packages are utilized for their applications. It creates a more predictable environment.